1. Field of the Invention
The present invention relates generally to medical methods, apparatus, and kits. More particularly, the present invention relates to methods, systems, and kits for percutaneously delivering implantable articles, such as subcutaneous drug inserts, to solid tissue locations.
Implantable articles are useful for a wide variety of medical purposes. Of particular interest to the present invention, drug inserts and controlled release reservoirs may be subcutaneously implanted in order to release a drug or other biologically active substance over time. Usually, the insert or reservoir will be implanted intramuscularly or intraperitoneally by first forming an incision which permits the article to be implanted at the target site. Often, a large bore needle or cannula is used to inject the insert or reservoir to the target location. Such devices, however, often result in coring of the tissue, and subsequent injection of the drug insert pushes against such cored tissue, rendering placement difficult. While such problems have been at least partly overcome by the use of trocar/cannula assemblies where the trocar cuts through tissue, the use of relatively large diameter trocars is traumatic to the patient and can leave scarring.
An improvement over the use of large diameter needles and trocars is proposed in U.S. Pat. No. 5,304,119. The xe2x80x2119 patent teaches use of a tapered cannula having a pair of opposed tines overs its distal end. The tines meet together in a xe2x80x9cduck billxe2x80x9d fashion and may be advanced through solid tissue with reduced trauma to the patient. After initial placement of the cannula, a drug insert may be advanced axially through the device, forcing the opposed tines to open and permitting placement of the insert at the desired target location. While workable and an improvement over prior delivery systems, reliance on passage of the drug insert to open the opposed tines can be problematic. In particular, the mechanical action can physically damage the drug insert prior to its delivery to the tissue target site.
For these reasons, it would be desirable to provide improved methods, systems, and kits for delivering implantable articles, such as drug inserts and controlled release reservoirs, to solid tissue locations. In particular, it would be desirable to provide for percutaneous delivery of such articles in a manner which is both minimally traumatic to the patient and minimally damaging to the article. At least some these objectives will be met by the invention described hereinafter.
2. Description of the Background Art
A device and method for injecting implants are described in U.S. Pat. No. 5,304,119, discussed in more detail above. Radially expanding dilators of a type suitable for use in the methods of the present invention are described in U.S. Pat. Nos. 5,183,464 and 5,431,676, and are commercially available under the tradename STEP from InnerDyne, Inc., Sunnyvale, Calif., assignee of the present application. Other pertinent patents include U.S. Pat. Nos. 5,674,240; 5,484,403; 5,403,278; 5,201,756; 4,899,729; 4,716,901; and 3,788,318.
According to the present invention, improved methods, systems, and kits are provided for implanting articles in solid tissue. The articles will usually be intended for drug delivery, typically being drug delivery inserts or reservoirs intended for controlled release of the drugs, but could also be intended for other purposes such as the delivery of brachytherapy seeds, pacemakers and other stimulatory devices and leads, pumps, transducers and other diagnostic and monitoring devices, sensors, and the like. The methods and systems of the present invention are characterized by the formation and radial expansion of a tissue tract from the surface of a patient""s skin to a target site beneath the skin, typically within solid tissue (e.g., muscle), beneath the peritoneum, (i.e., the retroperitoneum), or the like. The tissue tract is radially expanded, preferably, to a substantially constant lumen diameter over its entire length, with the expansion occurring prior to introduction of the drug insert or other article. Radial expansion of the tissue tract is generally less traumatic to the patient than use of a large bore coring needle or large diameter trocar, and full expansion of the tissue tract prior to introduction of the article avoids the risk of damage to the article which can occur with systems such as that described in U.S. Pat. No. 5,304,119, where the article itself mechanically opens a path as it is advanced.
In a first aspect, a method according to the present invention comprises percutaneously inserting a radially expandable sleeve so that a distal end of the sleeve lies adjacent to a target site in solid tissue. An assembly comprising a cannula and a dilator is then introduced through the radially expandable sleeve, where the cannula and dilator have a diameter which is larger than an initial diameter of the sleeve so that the sleeve is radially expanded as the assembly is advanced distally through a lumen of the sleeve. Usually, the dilator will have a tapered or pointed distal end which facilitates advancement through the sleeve and which can extend beyond the distal end of the sleeve to penetrate the solid tissue and create a potential space for receiving the article to be implanted.
After the cannula/dilator assembly has been fully advanced within the sleeve, the dilator is removed from the cannula, leaving the cannula in place to maintain an open lumen having a diameter which is significantly greater than the initial lumen diameter of the sleeve. Usually, the lumenal diameter of the cannula will be in the range from 2 mm to 20 mm, preferably from 3 mm to 12 mm, most typically from 3 mm to 5 mm, while the initial lumen diameter of the sleeve will be less than 1 mm. After the dilator has been removed from the cannula, the article is advanced distally through the cannula lumen and beyond the distal end of the cannula so that it enters into the tissue where it is to be implanted. Conveniently, the article can be advanced using the same dilator which was originally used to advance the assembly of the cannula and dilator. Alternatively, a separate pusher rod or other element may be provided for insertion, advancement, and implantation of the article.
Usually, the percutaneous sleeve inserting step will comprise advancing an assembly of the sleeve and a needle directly into the tissue. The needle will usually be a small diameter, non-coring needle having a sharpened distal tip which extends distally of the sleeve to facilitate advancement of the assembly through the tissue. The needle may then be withdrawn proximally from the sleeve, leaving the sleeve in place to receive introduction of the assembly of the cannula and dilator in a subsequent step. In the exemplary embodiment, the expandable sleeve comprises a tubular braid formed from a mesh of non-elastic filaments which axially shorten as they are radially expanded.
The article will preferably be a drug delivery implant or controlled and sustained release reservoir. The article may be used for delivering a wide variety of drugs of the type which are suitable for subcutaneous intramuscular implantation, such as contraceptives, hormonal replacement, e.g. estrogen, progesterone, testostoronen, and the like.
In a second aspect, the method of the present invention comprises radially expanding a tissue tract to form a lumen having a substantially constant diameter over its entire length. The article to be implanted is then advanced distally through the lumen after the lumen has been substantially completely expanded. In this way, patient trauma is reduced while the risk of damage to the implanted article is minimized.
The present invention further comprises kits including a radially expandable sleeve, a cannula, and a dilator. The kit will further comprise instructions for use setting forth any of the methods described above. The kit usually will further comprise a container for holding the various kit components together, typically being a pouch, tray, box, tube, or the like. The kit components will usually be sterilized and maintained sterilely within the packaging, where sterilization can be effected by conventional means, such as radiation, exposure to ethyleneoxide, or the like. Optionally, the kit may further comprise the article to be implanted, typically being a pharmaceutical implant or reservoir.
The present invention still further comprises systems including both a radially expandable sleeve and a drug delivery article. The radially expandable sleeve will be expandable from a narrow diameter configuration which can be percutaneously introduced to the patient with lessened patient trauma and which will be radially expandable to a large diameter configuration in order to provide a non-collapsible lumen. The drug delivery article will have peripheral dimensions which permit it to be delivered through the non-collapsible lumen of the sleeve after radial expansion. The lumen of the sleeve will be capable of remaining fully open to its large diameter configuration even in the absence of the article so that the article may be passed through the lumen without the need for the article to help open the lumen. Usually, the radially expandable sleeve will be opened using an assembly of a cannula and a dilator as generally described above.